May 5, 1943 is one of the most important dates, and possibly the least known, in the history of the nuclear age. It was the date when the first atomic bomb targeting decision was made — a full two years before the end of World War II in Europe.
The Military Policy Committee, the ultra-secret Manhattan Project’s de facto executive committee met that day to review progress. It also made the first decision regarding the use of the bomb: it should be used so it would land in water if it turned out to be a dud. And Germany would not be targeted; it would be the Japanese, who it was felt “would not be so apt to secure knowledge from it as would the Germans” (quote from a summary of the May 5 meeting). [After all, one of the world’s greatest physicists, Werner Heisenberg, was living in Nazi Germany.] So the Japanese fleet at the Pacific island of Truk was selected as the first target of the bomb; it met the criteria.
Later, in the fall of 1944, when scientists were certain that the uranium bomb would work, planning began for the use of the bomb on Japan. It was helped by the fact that Saipan had been conquered by July 9, 1944; Japan could be directly bombed from there using B-29 bombers. As Groves stated when he briefed the newly installed President Truman in April 1945, “The target is and was always expected to be Japan.”
Many of Manhattan Project’s scientists were European Jews motivated by a fear of a Nazi atomic monopoly. Ironically, they were completely unaware that Germany had been ruled out as a target two years before the war in Europe ended.
When the US atomic spy mission, called Alsos, confirmed in early December 1944 that Germany had no viable bomb project, the project was not stopped; rather it was accelerated. Joseph Rotblat was the only Project scientist who left at that time; he was to win a Nobel Peace Prize for that and later efforts to rid the world of nuclear weapons. Decades later, the great physicist, Richard Feynmann, wondered why he had continued work and not thought about the fact that the purpose of the Project had been accomplished when the war in Europe ended.
A very real and reasonable fear of a Nazi nuclear monopoly had been central to Einstein’s recommendation that President Roosevelt initiate an atomic bomb project. Apparently no one thought to ask what might occur if the United States wound up with the atomic monopoly. The answer came, of course, on August 6 and August 9, 1945 when Hiroshima and Nagasaki were obliterated.
Like many I have concluded that the bombings were unjustified, though that is an opinion far from universally held. But some of my reasons may surprise you. I explained them in a talk I gave in Santa Fe in 2012, entitled From Pearl Harbor to Hiroshima.